Every operation aims to employ a blasting system with the lowest possible operating cost. A common belief among operators is to utilise the least expensive explosive possible. However, the choice of explosive will affect the cost of the explosives and their loading and initiating systems in the blasting subsystem as well as the drilling, secondary breaking, loading, hauling, and crushing subsystems.
Cost of explosives
In general, the least expensive energy per unit is ANFO. The price of slurry can be somewhat more than that of ANFO or around four times higher. Less expensive slurries or emulsions don’t contain expensive, high-energy ingredients and are made for usage in blast holes with a big diameter. Their energy content is low relative to their weight. Slurries intended for small diameter application and high-energy products with significant aluminium or other high-energy constituent content are the costliest types.
The price of explosives made with nitro-glycerine can vary from three to five times that of an ANFO, primarily due to the amount of nitro-glycerine or other substances used. Because of a number of drawbacks, ANFO is not always the appropriate product for the job, despite its great economics. ANFO is not resistant to water, has a low specific gravity, and tends to explode inefficiently in unfavourable field conditions. Higher energy explosives could be more appealing, though, depending on the site’s characteristics.
Cost of drilling
The blaster should choose the least expensive explosives that will provide sufficient, consistent fragmentation under typical drilling conditions. However, controlled experimentation should be used to optimise both the cost of explosive and the cost of drilling when drilling prices rise, which is usually the case in hard, dense rock. Although explosives with a high energy density are typically more expensive, the blaster will want to boost the explosive’s energy density when drilling is costly. A slurry’s or emulsion’s energy density is determined by the density and percentage of high-energy elements, like aluminium, that are included into the mixture. The usage of high-energy goods requires careful consideration because to the wide range of slurries and emulsions available.
High velocity pneumatic loading can raise the density of ANFO in tiny diameter blastholes by up to 20%. Because of the empty space between the cartridge and the borehole wall, densified ANFO cartridges have a loading density (weight per metre of blasthole) that is comparable to bulk ANFO. Finely split aluminium can be added to ANFO to boost its energy density. Slitting cartridges before dropping them into the perforations will improve the explosive charge density of cartridges per metre. When the rock is harder to drill and blast, the economics of higher energy density explosives slurry, or emulsion, improve.
